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March 4 - 7, 2018

Hilton Phoenix / Mesa Hotel

Mesa, Arizona

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Future Fabrication - Advanced PCB Technology BiTS 2018 Session 2B Presentation 1

March 4-7, 2018 Burn-in & Test Strategies Workshop www.bitsworkshop.org

3D Printed Space Transformers

Don Thompson

R&D Altanova

BiTS Workshop

March 4 - 7, 2018

Conference Ready

mm/dd/2014



The World is Shrinking

• Mobile devices are leading the charge for smaller packages

• Current standards are 0.4 mm pitch and 0.35 mm pitch

• Future standards are 0.3 mm and smaller

• In ATE, we are running into a wall on testing mobile parts

3D Printed Space Transformers 2

0.5 mm

0.4 mm 0.3 mm

BGA Packages WLCSP Probe

280 um

150 um 50 um



The Impact of Aspect Ratios


Device Pitch

0.5mm

0.4mm

0.35mm

0.3mm

0.65mm

Via Diameter Board Thickness

8 mil Via Drill

(0.2 mm)

6 mil Via Drill

(0.15 mm)

5 mil Via Drill

(0.125 mm)

10 mil Via Drill

(0.25 mm)

Aspect Ratio

250 mils

(6.25 mm)

200 mils

(~5 mm)

140 mils

(~3.5 mm)

300 mils

(7.5 mm) 30

31

33

28

As p

itch S

hrinks

Your

Board

Must

Get T

hin

ne

r

OK

Broken



Via Construction Basics

Via plating is limited by fluid dynamics

Therefore… physics limits aspect ratios


3. Via Plating 1. After Board Press 2. Via Hole is Drilled 4. Outer Layer Etch



Flip Drilling

• All high aspect ratio vias are done with flip drilling

• The longer the drills, the lower the board yield


1. After Board Press 2. Drill from top 3. Drill from bottom

mid mid

Drill Wander

mid



PCB Drill Bits

• PCB drill bits

– 0.25 mm drill shown

• There is a trade off

between throat depth and

drill wander


Throat Depth



PCB Manufacturing Challenges

• Via plating

• Via drilling accuracy

• Alignment between layers

The PCB industry has worked very hard to improve these

tolerances and there isn’t much room for improvement




What is the Industry Solution for 0.3 mm pitch?

The market uses one of two different solutions:

1. Dual lamination (Same as 2 but built into the same board)

or

2. Space transformer (also known as Multi Layer Organic - MLO, Multi Layer

Ceramic - MLC, or substrate) – Space transformers are made using a more accurate fabrication process


Probe Card

Space transformer

Tester

Smaller more

accurate PCB



Space Transformer Challenges

• Expensive build process

– Require build up layers

– Buried vias

– Very fine etch tolerances

• Typically require narrow trace (~25 micron)

– Increased losses

– Poor impedance control

• High cross talk

• Two stage design process


Expensive &

Long fab time



Yes But… What Choice Do We Have?


“The shortest path is the one you know.”

The current method works, but it’s

1. Expensive

2. Slow

3. Takes a lot of design resources



What If We Could Build Angled Vias?


• Space transformers are hard because the angled path must be routed on

Cartesian lines

• If we can used angled lines, space transformers become trivial



3D Printed Space Transformers

• Developed a 3D printing process for space transformers

• Currently capability 0.3 mm pitch

– Future technology will allow us to go smaller!

• Custom software driven design




3D Printing Flexibility

• Vias can be shapes, curves, or angled

• Signals can be routed like PCB traces in 3D space

• Signal nets can be coaxial or impedance tuned

• Power nets can be merged together, made thicker, or

designed for low inductance

• Printed blocks can be as tall as 4” high

• This technology is young and will have a fast improvement

curve, enabling smaller features and better tolerances




Prototype Shown Below

• 0.5 mm to 0.3 mm transform

• 15 x 15 staggered pitch

• 421 pins

• 0.100” tall

• Solder attachable

(Transparent dielectric used

for demonstration purposes)


0.5mm pitch

0.3mm pitch



The Impact of Aspect Ratios


Device Pitch

0.5mm

0.4mm

0.35mm

0.3mm

0.65mm

Via Diameter Board Thickness

8 mil Via Drill

(0.2 mm)

6 mil Via Drill

(0.15 mm)

5 mil Via Drill

(0.125 mm)

10 mil Via Drill

(0.25mm)

Aspect Ratio

250 mils

(6.25mm)

200 mils

(~5 mm)

140 mils

(~3.5 mm)

300 mils

(7.5mm) 30

31

33

28

As p

itch S

hrinks

Your

Board

Must

Get T

hin

ne

r

A 0.5 mm pitch allows for a

PCB of at least 250 mils thick!



Standard Use Model: Reflow on ATE Board

Underfill

0.5mm Pitch Load Board

Space Transformer is reflowed onto board and socket is assembled on top

2. Attach Socket


1. Reflow Space Transformer

0.3mm pitch

0.3mm pitch 0.5mm pitch



Advantages for 0.3 mm Pitch

• Allows for a ≥ 0.250” thick main board – More PCB layers

– Better signal integrity (SI), Better power integrity (PI)

– Easier back drills

– Better board yield

– Higher site count (More routing resources & bigger “sweet spot”)

• Space Transformer – Easy design

– Fast build time




Disadvantages

• PCBs scale better than 3D printing

– Long individual build time, less parallel manufacturing benefits

• Edge tolerances are worse than PCB edge tolerances

• No power or ground planes




Conclusion

• Space transformers are a revolutionary solution for an

emerging 0.3 mm pitch problem

– This is only one application of this technology and we’re

investigating other uses

– This has never been done before and this suggests possibilities

as limitless as PCBs themselves


march 4 - testconx | connecting electronic test ... · session 2b presentation 1 burn-in & test...

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